1862.] RAMSAT GLACIAL OEIGrN" OF LAKES. 201 



course of glaciers filling valleys that extend right into the heart of 

 the mountains. 



8th. Most of the lakes are broad or deep according to the size of 

 the glaciers that flowed through the valleys in which they he, this 

 general result being modified according to the nature of the rock and 

 the form of the ground over which the glacier passed. Thus, the long 

 and broad Lake of Geneva, scooped in the Miocene lowlands, is 984 feet 

 deep, and over its area once spread the broad glacier of the Ehone. 

 Its great breadth and its depth evince the size of the glacier that over- 

 flowed its hollow. The Lake of Constance, lying in the same strata, 

 and equally large, is 935 feet deep, and was overspread by the equally 

 magnrficent glacier of the Upper Ehine. The Lakes of Maggiore and 

 Como, deepest of all, lie in the narrow valleys of the harder 

 Secondary rocks of the older Alps ; and the bottom of the first 

 is 1992 feet, and the latter 1043 feet, below the sea-level. 

 Both of these he within the bounds of that prodigious system 

 of glaciers that descended from the east side of the Pennine 

 Alps and the great ranges north and south of the Yal TeUina, and 

 shed their moraines in the plains of Piedmont and Lombardy. The 

 depth of the lakes corresponds to the vast size and vertical pressure 

 of the glaciers. The circumstance that these lakes are deeper than 

 the level of the sea does not afi'ect the question, for we know nothing 

 about the absolute height of the land during the Glacial period. 



The Lakes of Thun and Brienz form part of one great hoUow, 

 more than 2000 feet deep in its eastern part, or nearly 300 feet 

 below the level of the sea. They lie in the course of the ancient 

 glacier of the Aar, the top of which, as roches moutonnees and 

 striations show, rose to the very crests of the mountains between 

 Meyringen and the Grimsel. 



The Lake of the Four Cantons is imperfectly estimated at only 

 884 feet in depth ; but here we must also take into account the great 

 height and steep inclines of the mountains at its sides. The Lake of 

 Zug, 1311 feet deep, lies in the course of the same great glacier, the 

 gathering-grounds of which were the slopes that bound the tributaries 

 of the Upper Eeuss and the immense amphitheatre of the Urseren 

 Thai, bounded by the Kroutlet, the Sustenhorn, the Galenstock, the 

 St. Gothard, and the southern flanks of the Scheerhorn. 



The lesser depths (660 feet) of the Lake of Zurich were hoUowed by 

 the smaller but still large glacier that descended the valley of the 

 Linth. 



This completes the evidence. 



Lcikes of the Northern Hemisphere generally. — ^I shall now make a 

 few remarks on the bearing of this subject on the glacial question 

 generally. 



It is remarkable that in Europe and North America, going north- 

 ward, lakes become so exceedingly numerous, that I have been 

 led to suppose the existence of some intimate connexion between 

 their numbers and the northern latitudes in which they occur. 



Let any one examine the map of North America, and he will 



